Converted-wave prestack migration and velocity analysis by equivalent offsets and CCP gathers

John C. Bancroft, Shaowu Wang

A theoretical method is presented to enable prestack migration and velocity analysis of converted wave data. It is based on a new method of P-P prestack migration using equivalents offsets and common scatter point (CSP) gathers. Equivalent offsets for converted wave data are defined for all samples that prestack migrate to a common conversion point (CCP). Samples from all the input traces are added to the appropriate offsets in the CCP gathers. Velocity analysis may be performed on the CCP gather using conventional velocity analysis tools such as semblance analysis. Migration is completed by NMO and stacking of the CCP gather.